This application is related to and claims priority from Japanese Patent Applications No. 2001-88588 filed on Mar. 26, 2001 and No. 2002-13999 filed on Jan. 23, 2002, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a vehicle air conditioner for performing a cold storage operation using power of a vehicle engine, and for cooling air to be blown into a passenger compartment by performing a cold release operation when the vehicle engine is stopped.
2. Description of Related Art
Recently, for environmental protection, an engine is automatically stopped in a vehicle such as an economy running vehicle and a hybrid vehicle when the vehicle is stopped at a traffic signal or the like. However, when a compressor is driven by power from the vehicle engine in a vehicle air conditioner, the compressor is also stopped every time when the vehicle is stopped at a traffic signal. Accordingly, temperature of an evaporator is increased, and temperature of air to be blown into the passenger compartment is increased. As a result, cooling feeling for a passenger in the passenger compartment may be deteriorated.
To overcome this problem, a cold storage operation can be performed using power from the vehicle engine while the vehicle travels, and thereafter, air to be blown into a passenger compartment can be cooled by performing a cold release operation while the vehicle stops. However, when the vehicle is stopped for a long time, a cold storage amount becomes deficient, and cooling feeling for the passenger in the passenger compartment is deteriorated. On the contrary, when the vehicle is stopped for a short time, the cold storage amount becomes excessive, and power consumed in the vehicle engine is increased.
In view of the above problems, it is an object of the present invention to provide a vehicle air conditioner which improves cooling feeling for a passenger while a vehicle engine is stopped, and reduces power consumed in the vehicle engine by suitably controlling a cold storage amount.
According to the present invention, in an air conditioner for a vehicle having a navigation unit for searching vehicle-travel state information and road information, the air conditioner includes an evaporator for cooling air to be blown into a passenger compartment, a compressor driven by power of a vehicle engine, a cold storage unit for performing a cold storage operation using cooling operation of the evaporator, and a control unit for controlling cooling temperature of the evaporator. In the air conditioner, when the vehicle engine is driven, the control unit selects one of a cold storage mode where the cooling temperature of the evaporator is made lower than a predetermined temperature so that the cold storage operation in the cold storage unit is performed, and a normal cooling mode where the cooling temperature of the evaporator is higher than that in the cold storage mode. On the other hand, when the vehicle engine is stopped, the control unit selects a cold release mode where air is cooled by using cold release operation from the cold storage unit. The control unit estimates a necessary time period from a present time to a time at which the vehicle is stopped next, and a vehicle stopping time period from the time at which the vehicle is stopped next and a time at which the vehicle is re-started, based on the vehicle-travel state information and the road information searched by the navigation unit. Further, the control unit calculates a necessary cold release amount necessary for cooling in the vehicle-stopping time period based on the estimated vehicle-stopping time period, and controls operation of the cold storage mode so that the cold storage is performed in the necessary time period by a cold storage amount corresponding to the necessary cold release amount. Accordingly, the cold storage amount can be suitably controlled in accordance with the vehicle-stopping time period, so that cooling feeling for a passenger can be improved while the vehicle is stopped, and power consumed in the vehicle engine can be effectively reduced.
Recently, the present position of the vehicle, a travel direction thereof and a vehicle speed can be detected using Global Positioning system (GPS), a gyro and the like. Further, a navigation unit and the like include map information having traffic-signal position information. In the future, the navigation unit will include operation notice information for indicating a time for which a signal changes between red and green. Thus, the navigation unit includes a travel state detection device for detecting the travel state information having at least a vehicle present position, a vehicle-travel direction and a vehicle travel speed, and the navigation unit has traffic signal information for indicating a traffic signal position and a switching operation thereof. Preferably, while the vehicle is in travelling, the necessary time period and the vehicle stopping time period are estimated based on the travel state information and the traffic signal information. Accordingly, the necessary time period and the vehicle stopping time period can be more accurately estimated.
Preferably, the compressor is disposed to recover inertial power of the vehicle using the cold storage operation of the cold storage unit when the compressor is driven by the inertial power, the control unit estimates a time zone for which the inertial power is recovered among the necessary time period, based on the vehicle-travel state information and the traffic signal information, and the cold storage mode is preferentially performed in the time zone among the necessary time period. Therefore, the inertial power can be effectively used, and the power consumed in the vehicle engine can be further reduced.
In a case where the vehicle has a generator driven by one of the power of the vehicle engine and the inertial power, and has a battery unit charged by the generator, the control unit controls charging operation of the battery unit to charge necessary electric power required to start the vehicle in the battery unit at least in the necessary time period, the control unit estimates rotational speed fluctuations of the compressor and the generator in the time zone based on the vehicle-travel state information and the traffic signal information, and the control unit calculates operational efficiency fluctuations of the compressor and the generator in the time zone using the rotational speed fluctuations, respectively. In this case, when an actual cold storage amount of the cold storage unit is smaller than the necessary cold release amount and a charging power of the battery unit is smaller than the necessary electric power, the compressor and the generator are driven while the time zone is divided into a drive time zone of the compressor and a drive time zone of the generator, so that the inertial power is recovered at each high operational efficiency of the compressor and the generator, higher than a predetermined level.
When the vehicle includes vehicle speed detection means for detecting vehicle speed information related to a vehicle speed, and a memory member for storing the vehicle speed information, when it is estimated, based on the past vehicle speed information stored in the memory member, that the vehicle travels on a city road in which the vehicle is stopped at every predetermined time, the control unit selects the cold storage mode. Because it can be more accurately determined whether the vehicle travels on a city road and the cold storage mode is performed when the vehicle travels on a city road, cooling feeling for the passenger can be effectively improved while the vehicle is stopped on the city road, and engine power can be saved. Preferably, the control unit beforehand sets a specific fluctuation pattern of the vehicle speed as a fluctuation pattern of the vehicle speed on a city road. In this case, when the past fluctuation pattern of the vehicle for a past predetermined time is similar to the specific fluctuation pattern, the control unit estimates that the vehicle travels on a city road. Alternatively, the control unit calculates an average vehicle speed for the past predetermined time based on the vehicle speed information. In this case, when the average vehicle speed is lower than a predetermined vehicle speed, the control unit estimates that the vehicle travels on a city road. Alternatively, the control unit calculates a number of vehicle stop for a past predetermined time, based on the vehicle speed information. In this case, when the number of vehicle stop is more than a predetermined number, the control unit determines that the vehicle travels on a city road.
Further, in the air conditioner, when it is estimated that the vehicle is on a city road based on a vehicle present position and map information, the cold storage mode is selected. In this case, it can be more accurately determined whether the vehicle travels on a city road. Therefore, cooling feeling for the passenger can be effectively improved while the vehicle is stopped, and engine power can be saved.
Preferably, the control unit calculates a distance between neighboring traffic signals around the present position of vehicle based on the present position of the vehicle and the map information. In this case, when the distance is shorter than a predetermined distance, the control unit estimates that the vehicle is on a city road. Alternatively, the control unit beforehand sets a specific area as a city road in the map information. In this case, when the vehicle is in the specific area, the control unit estimates that the vehicle is on a city road.